1. Field of the Invention
2. Prior Art
Metal milling machines have been around for many years. One very common one is the Bridgeport type universal standard vertical milling machine. This type of milling machine may be characterized by a vertical spindle, which spindle is manually activated by a handle, to pull a tool towards and push it away from a surface to be worked.
In a Bridgeport type universal milling machine, a collet is utilized to hold a specific tool. The collet is removed and a new collet is put in its place in the spindle, with a new tool in the new collet. The collet provides a machined surface so as to accurately mate with the spindle, thereby maintaining accuracy of the tool during its milling operation. Such a collet may be known under its common name as an "R-8" collet.
In a standard universal Bridgeport type universal milling machine, to release a tool therefrom, a draw bar, which extends through the spindle at the top of the machine head, has to be turned, so as to unscrew the lower end of the draw bar from the existing collet within the lower end of spindle. As the draw bar is unscrewed, the collet is pushed downwardly and the top of the draw bar is given a sudden sharp blow by a heavy object such as a wrench or a hammer. The collet is thus freed from the grip of the lower end of the spindle, and a new collet with a new tool therein, is put into the chuck of the spindle and the new collet is tightened into place by turning the top of the draw bar which turns the lower end of the draw bar into the female portion of the top of the collet. Such an operation can take between one and two minutes to complete in order to successfully change a tool in a vertical milling machine.
There are a number of patents amongst the prior art, which attempt to show arrangements for changing a tool in a milling machine. One such arrangement is shown in U.S. Pat. No. 2,135,861 issued to Thompson. This particular arrangement is for a broaching machine, and would not be utilized with a rotary milling machine inasmuch as it would gall any rotary member utilized therein.
U.S. Pat. No. 3,674,281 issued to Hedrick shows a tool chuck assembly with a spring which is utilized to press a ball against a wire/tool within a tapered cup. The spring however, is not pulling on the tool itself, it is utilized only for wedging engagement of a ball against the tool. U.S. Pat. No. 4,171,821 issued to Miller shows a quick change collet tool holder assembly. A spring however, merely holds the outside of a sleeve in position. This spring is not utilized to locate and position the tool in place. U.S. Pat. No. 4,322,190 issued to Anderson shows a mounting device for machining tools wherein a ball and a bar locking engagement to secure a milling cutter on the end of a spindle nose. U.S. Pat. No. 4,743,145 issued to Hendricks et al. shows a quick change drill chuck system which utilizes a hydraulic system for changing a nose piece of a tool. U.S. Pat. No. 4,768,282 issued to Reick et al., shows a tooling quick release change apparatus for a metal working machine. This arrangement permits the elimination of a draw bar mechanism commonly used in standard metal working machines.
It is the object of the present invention however, to provide a "Bridgeport" type universal vertical milling machine, having a manual tool advance arrangement, with a quick tool change mechanism for larger tools, which will also prevent the tools from coming loose.
It is yet a further object of the present invention, to provide a quick tool change mechanism which will be readily retrofittable in existing "Bridgeport" type "kneemill" manual universal vertical milling machines utilizing R-8 type collets.
It is yet still a further object of the present invention, to provide a quick tool release mechanism which will maintain tool accuracy and alignment after changing from one tool to another, while insuring that the tool will not slip or kick out.
Therefore, it is the object of the present invention, to provide an apparatus for retrofitting existing vertical type milling machines to permit them to have their tools changed and maintained more securely in the spindle, in a fraction of the time than it presently takes.